1. Field of the Invention
This invention generally relates to an image sticking elimination circuit, and more particularly to an image sticking elimination circuit suitable for supplying charged power to display panel and driving circuit when an abnormal power shut down occurs.
2. Description of Related Art
Liquid crystal material was discovered by Europe, developed by the US, and applied by Japan in several fields. Currently, several liquid crystal technologies have been widely used in displays, especially for liquid crystal displays (LCD). The LCD has been developed from TN-LCD, STN-LCD, to TFT-LCD. Some manufacturers also begin to develop LPTS-LCD.
FIG. 1 is a conventional LCD panel. The LCD panel 100 includes a gate driving circuit 110, a data driving circuit 120, a plurality of gate lines 112, a plurality of data lines 122 and a plurality of pixel units 130, wherein each of the pixel units 130 comprises a transistor 132, a capacitor 134 and a liquid crystal cell 136. When the data is written (i.e., when the data is going to be displayed on the LCD panel 100), the gate driving circuit 110 will raise the gate line 112 from a low voltage level to a high voltage level so that the transistor 132 will be turned on. Then the data driving circuit 120 writes the data to the capacitor 134 via the data line 122. After the data is written into the capacitor 134, the gate driving circuit 110 will raise the gate line 112 from a high voltage level to a low voltage level so that the liquid crystal cell 136 can continue to display the data before the next data is written. However, when the abnormal power-off on the LCD panel 100 occurs, the data is still retained in the capacitor 134. That is where the image sticking comes from.
The conventional method to eliminate or reduce the image sticking is to shift the I-V curve of the transistor 132 (as shown in FIG. 2) to the left so that the threshold voltage of the transistor 132 is close to 0V. Hence the transistor 132 can be turned on even if the gate voltage of the transistor 132 is close to 0V so that the data stored in the capacitor 134 can be released to the data line 122.
However, to have a better resolution, one may not shift the I-V curve as he wishes because it also affects the circuits in the LCD panel 100. Hence, the image sticking issue cannot be solved by the conventional method without affecting the resolution of the LCD panel.